1. Field of the Invention
The invention relates to well drilling and completion, and to an apparatus and methods for use with expandable tubulars. Generally, the invention relates to a liner hanger and a method of hanging a liner.
2. Background of the Related Art
In the oil and gas exploration and production industry, bore holes are drilled in the earth to access hydrocarbon-bearing formations. The drilled bores are lined with steel tubing, known as casing or liner, which is cemented in the bore. After a certain depth is reached, drilling is halted and a well casing is lowered down the wellbore and cemented in place. Typically, drilling resumes in the wellbore until a next predetermined depth is reached. At this stage, drilling is halted and a liner is lowered down the well casing. The liner is suspended from the well casing or from a previous string of liner by a liner hanger which utilizes slips and cones and acts between the liner and the well casing. The purpose of casing and liner is to provide support to the wellbore and facilitate isolation of certain parts of the wellbore.
The liner can be set mechanically or hydraulically. A typical apparatus for setting a liner in a well casing includes a liner hanger and a running tool. The running tool is provided with a valve seat obstruction which will allow fluid pressure to be developed to actuate the slips in order to set the liner hanger in the well casing. Once the liner hanger has been set, the running tool is rotated anti-clockwise to unscrew the running tool from the liner hanger and the running tool is then removed.
A recent trend in well completion has included expandable tubular technology. Both slotted and solid tubulars can be expanded in situ to enlarge a fluid path through the tubular and also to fix a smaller tubular within the inner diameter of a larger tubular therearound. Tubulars are expanded by the use of a cone-shaped mandrel or by an expansion tool with expandable, fluid actuated members disposed on a body and run into the wellbore on a tubular string. During expansion of a tubular, the tubular walls are expanded past their elastic limit. Examples of expandable tubulars include slotted screen, joints, packers, and liners. FIG. 1 is an exploded view of an exemplary expansion tool 100. The expansion tool 100 has a body 102 which is hollow and generally tubular with connectors 104 and 106 for connection to other components (not shown) of a downhole assembly. The connectors 104 and 106 are of a reduced diameter compared to the outside diameter of the longitudinally central body part of the tool 100. The central body part has three recesses 114 to hold a respective roller 116. Each of the recesses 114 has parallel sides and extends radially from a radially perforated tubular core (not shown) of the tool 100. Each of the mutually identical rollers 116 is somewhat cylindrical and barreled. Each of the rollers 116 is mounted by means of an axle 118 at each end of the respective roller and the axles are mounted in slidable pistons 120. The rollers are arranged for rotation about a respective rotational axis which is parallel to the longitudinal axis of the tool 100 and radially offset therefrom at 120-degree mutual circumferential separations around the central body. The axles 118 are formed as integral end members of the rollers and the pistons 120 are radially slidable, one piston 120 being slidably sealed within each radially extended recess 114. The inner end of each piston 120 is exposed to the pressure of fluid within the hollow core of the tool 100 by way of the radial. perforations in the tubular core. In this manner, pressurized fluid provided from the surface of the well, via a tubular, can actuate the pistons 120 and cause them to extend outward and to contact the inner wall of a tubular to be expanded. Additionally, at an upper and a lower end of the expansion tool 100 are a plurality of non-compliant rollers 103 constructed and arranged to initially contact and expand a tubular prior to contact between the tubular and fluid actuated rollers 116. Unlike the compliant, fluid actuated rollers 116, the non-compliant rollers 103 are supported only with bearings and they do not change their radial position with respect to the body portion of the tool 100.
One use for expandable tubulars is to hang one tubular within another. For example, the upper portion of a liner can be expanded into contact with the inner wall of a casing in a wellbore. In this manner, the bulky and space-demanding slip assemblies and associated running tools can be eliminated. One problem with expandable tubular technology used with liners relates to cementing. Cementing is performed by circulating the uncured cement down the wellbore and back up an annulus between the exterior of the liner and the borehole therearound. In order for the cement to be circulated, a fluid path is necessary between the annulus and the wellbore. Hanging a liner in a wellbore by circumferentially expanding its walls into casing seals the juncture and prevents circulation of fluids. In order to avoid this problem, liners must be either temporarily hung in a wellbore or, more preferably, partially expanded prior to cementing whereby the liner is suspended in the casing but a fluid path remains back to the surface of the well. The problem is usually addressed by partially expanding the liner in order to hang it in the wellbore and then finishing the expansion after the cementing is done but prior to the curing of the cement. However, the tools for expanding tubulars are typically designed to expand the tubular in a circumferential fashion and cannot be effectively used to only partially expand the tubular.
Therefore, there is a need for a liner hanger apparatus and method that permits a liner to be hung in a well and also permits a fluid path around the liner, at least temporarily. There is a further need for a liner hanger that can be partially expanded into a casing but leaves a fluid path therearound. Additionally, there is a need for improved expandable liner hangers with a means for circulating fluids therearound.
Therefore, there is a need for a liner hanger appartus and method that permits a liner to be hung in a well and also permits a fluid path around the liner, at least temporarily. There is a further need for a liner hanger that can be partially expanded into a casing but leaves a fluid path therearound. Additionally, there is a need for improved expandable liner hangers with a means for circulating fluids therearound.